By default columns for both longitude and latitude can be selected. In addition if a geojson is provided then a chloropleth will be rendered on the map where the colour is based on the number of samples within each geoJSON boundary
As an alternative to longitude and latitude, a single column for ISO 3166 codes can be provided. For country level (3166-1) codes any 2 letter from the official 3166-1 list can be used. For the UK and USA 2 letter codes from the the 3166-2 lists can be used.
If you would like to add more lon/lat codes for other country 3166-2 codes please send a pull request for this file.